Silicated soda ash

ABSTRACT

A method of preparing a particulate detergent builder includes admixing liquid sodium silicate with anhydrous soda ash having a particle size of less than 200 microns at a temperature between 21*-51*C., passing the resultant wetted granules through at least an eight mesh screen and rapidly heating the screened material to in excess of 100*C.

nited States Patent [191 Temple v 11] 3,821,119 June 28, 1974 1SILICATED SODA ASH [75] Inventor: Ralph E. Temple, Chardon, Ohio [73]Assignee: Diamond Shamrock Corporation,

Cleveland, Ohio [22] Filed: May 3, 1972 [21] Appl. No.: 250,031

[52] US. Cl. 252/135, 252/385 [51] InLCI. Cl1d3/08,C11d 3/10 [58] Fieldof Search 252/135, 385, 99

[5 6] References Cited UNITED STATES PATENTS 2,099,743 11/1937 Kroeger252/175 X 2,333,443 11/1943 Robinson. 252/135 2,351,559 6/1944 Treffler.252/135 2,365,215 12/1944 Rhodes 252/135 X 2,515,880 8/1950 MacMahon252/1-35 2,909,490 10/1959 Metziger 252/135 3,247,1 18 4/1966 Matthaei252/99 3,285,859 11/1966 .lelen 252/385 3,620,979 11/1971 Corlissetal...252/385 3,630,928 12/1971 Fuchs 252/135 FOREIGN PATENTS ORAPPLICATIONS 4,1 1 l 4/1912 Great Britain 494,628 10/1938 Great Britain525,514 8/1940 Great Britain Primary Examiner-Leon D. Rosdol AssistantExaminer-P. E. Willis Attorney, Agent, or Firm-Wi1liarn A. Skinner;Timothy Tinkler [57] ABSTRACT A method of preparing a particulatedetergent builder includes admixing liquid sodium silicate with anhy- 3Claims, No Drawings SILICATED SODA ASH It is known to be desirable toincorporate alkali metal silicates into various detergent compositionsboth for their inherent detergency and for their ability to protectceramic and reactive metal surfaces from corrosive attack. Variousproblems have presented themselves in attempting to effect thisincorporation. The most readily available source of dry, granularsoluble SiO is the crystalline sodium metasilicates which, however, aretoo alkaline for many uses and in any event tend to segregate from thecompositions into which they are incorporated. Other particulate sodiumsilicates having a higher ratio of silica to sodium oxides are notreadily available, thus being too expensive for incorporation into mostdetergent compositions. Furthermore, where used, the tendency of theseparticulate materials is again tosegregate and/or contributesubstantially to dusting. Various techniques have been suggested forblending liquid silicates into a detergent composition followed bydrying to achieve the desired particulate state. However these methods,such as spray drying or agglomeration, generally require expensiveequipment and hence large scale production to justify the necessaryinvestment.

STATEMENT OF THE INVENTION Therefore it is an object of the presentinvention to provide a method for incorporating liquid silicates into adetergent formulation.

It is a further object of the present invention to provide a particulatesilicated soda ash and-a method of preparing same. i

There has now been found a method of preparing a free-flowingparticulate detergent builder, which method consists essentially of:

a. preparing an aqueous solution of sodium silicate having a Na O:SiOweight ratio of from 1:1.6 to 3.3 and a solids content of from 38 to 50percent by weight;

b. admixing said solution with a substantially anhydrous sodiumcarbonate having a particle size of less than about 200 microns, saidcarbonate constituting from 45 to 70 percent by weight of the mixture;

c. maintaining the temperature during admixture bed. after thoroughadmixing, passing the resultant material through at least an eight meshscreen;

e. rapidly heating the wetted, screened material to a temperature withinthe range of 105 to 250C.

and,

f. recovering as the product a substantially dry particulate detergentbuilder having a bulk density of from 25 to 50 pounds per cubic feet anda uniform SiO content of from to 30 percent by weight.

In such a detergent builder the silicate is distributed uniformly on thesoda ash particles and a sufficient amount of said silicate may beincorporated to provide the desired and advantageous properties. Furtherit has been found that the resultant particles are highly absorbent,being capable of taking up, for example, up to percent of their weightof a liquid surfactant. It will be appreciated that the equipmentrequirements of one desiring to produce such a detergent builder arequite modest. Hence, most any desired size production operation may beachieved.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The sodium silicate employedwill generally be one of those commercially available which have an NaO:SiO weight ratio within the stated range of from about l:l.6 to 3.3and a solids content within the range of from 38-50 percent by weight,the balance being water. Of course it is possible to adjust the ratio ofthe solution to a desired point by the addition of sodium hydroxide. Theamount of such a silicate employed will be within the range of from30-55 percent of the combined aqueous silicate/soda ash, correspondingto a uniform SiO content in the final product within the range of l0 to30, preferably 18-22, percent by weight.

The sodium carbonate must be substantially anhydrous since thosematerials having water bound thereto will not accept the desiredquantities of silicate. That the soda ash has a particle size of lessthan about 200 microns, for example passing through an eighty meshscreen, has been found important to the process since otherwise a stickymass, essentially impossible to mix while retaining a particulate form,will be obtained on addition of the silicate solution. The amount ofsodium carbonate employed falls within the range of 45 to percent byweight of the mixture.

It has been noted that during the admixture of the silicate and soda ashit is essential that the temperature be maintained within the range of 21 to 51C. At lower temperatures the mixture becomes quite heterogeneousconsisting of quantities of silicate coated with soda ash and free sodaash. On the other hand, at temperatures in excess of about 51C. ataffy-like mass is formed which is unsuitable for the subsequentoperations.

The result of the foregoing is a wet granular material which is thenpassed through at least an eight mesh screen in order to obtain aparticle size suitable for subsequent operations. By the phrase at leastan eight mesh screen it is intended to refer to an eight mesh screen(Tyler or US. Standard) or one the openings of which are smaller, e.g.,a 10 mesh screen.

The thus-screened material is then passed to a heating step wherein thetemperature is rapidly raised to within the range of to 250C. Forexample, the

material being screened may be allowed to fall directly onto the surfaceof a hot plate having the appropriate temperature. The purpose of theheating step is to cause the formation of water vapor within thesilicate and the subsequent release thereof, thereby resulting in theformation of a silicate foam. Temperatures of less than 105C. do notyield any substantial foaming, thus dictating a product having a bulkdensity higher than is generally desired for use as a detergent builder.While temperatures in excess of 250C. may be used, no significantadditional advantage is obtained, an optimum low bulk density beingachieved at the stated temperature. Obviously then, control of thetemperature within this range is one method of regulating the bulkdensity of the product within the stated range of 25 to 50, preferably35 to 50, pounds per cu. ft.

Itwill be apparent from the foregoing that, with the appropriate choiceof equipment, the process may be operated either batch-wise, for smallamounts with specific formulations, or, preferably, in a continuousmanner.

A surprising result of this process, and characteristic of the product,is that the pH of the silicated soda ash is lower than that of eitheringredient alone. For example, the pH (measured as a 1 percent aqueoussolution) of a product made from sodium silicate having a ratio of l:2.4and containing 20 percent Si is measured at 1 L0. A solution of soda ashalone reads 1 L4 and the silicate has a pH of l 1.3.

In order that those skilled in the art may more readily understand thepresent invention and certain preferred embodiments by which it may becarried into effect, the following specific examples are afforded.

EXAMPLE 1 ln the following Table the samples are prepared by adding thesilicate to the soda ash over a period of minutes while mixing at lowspeed in a Hobart mixer at a temperature of about 43C. The soda ashemployed is an anhydrous sodium carbonate, 98 percent of the particlesof which pass through an 80 mesh Tyler sieve, indicating a particle sizeof less than 174 microns. Mix- EXAMPIIE 3" scope of the appended claims.

I claim:

I. A method of preparing a free-flowing particulate silicated sodiumcarbonate detergent builder which method consists essentially of:

a. prearing an aqueous solution of sodium silicate having an Na O:SiOweight ratio of from 121.6 to 3.3 and a solids content of from 38-50percent by weight;

b. admixing said solution with substantially anhydrous sodium carbonatehaving a particle size of less than about 200 microns, said carbonateconstiture increase has essentially no further effect on the ultimatebulk density. Sample 8 was determined to be capable of absorbing up to15 percent of a liquid polyethoxy ether nonionic surfactant while stillremaining freeflowing.

By way of comparison, Sample 3 is repeated, substituting a commerciallyavailable anhydrous sodium carthssame esul s,

Upon grinding the first of the aforesaid commercial 5 soda ashes untilit passes through an eighty mesh screen, a satisfactory product similarto Sample 3 is obtained.

ing is continued for 10 minutes after addition is com- 25 tuting from 45to percent of the mixture; pleted, following which the wet granularmaterial is c. maintaining the temperature during admixture bescreenedthrough a l0 mesh Tyler sieve onto a hotplate tween 21 and 51C.; havingasurface temperature as indicated. n d. after thorough admixing, passingthe resultant ma- TABLE Na CO; Aqueous Na O:SiO, Silicate Drying ProductBulk Silicate Solids Tempera- SiO Density Sample (gms.) (gms.)(wt.ratio) (7r) ture (C.) (7:) (lbs/ft) By comparing Samples 1, 2 and 4of the Table, the terial through at least an eight mesh screen; effectof temperature in the drying step on the bulk e. rapidly heating thescreened material to a temperadensity of the product can be seen.Further, Sample 3 ture within the range of 105 to 250C. and, indicatesthat an additional and substantial temperae er ng as heproductasubstantially dry particulate detergent builder having a bulkdensity of from 25 to 50 pounds per cu. ft. and a uniform SiO contentfrom 10 to 30 percentby weight.

2. The particulate free-flowing silicated sodium carbonate detergentbuilder produced by the method of claim 1 which is a substantiallyanhydrous coherent mixture of sodium carbonate and a sodium silicatehaving a Na O:SiO ratio of 1:1.6 to 3.3, the amount of SiO being withinthe range of 10 to 30 percent, said builder having a bulk density withinthe range of 25 to 50 lbs./ft. being capable of absorbing up to 15percent of its weight of a liquid nonionic surfactant and having a pHlower than that of either the sodium silicate or sodium carbonate fromwhich it is fonned.

3. The particulate free-flowing silicated sodium carbonate detergentbuilder produced by the process of claim 1 containing from 18 to 22percent by weight SiO as sodium silicate having a Na O:SiO weight ratiol:2.4, said builder having a bulk density within the range of 35 to 50lbs/ft, being capable of absorbing about 15 percent of its weight of aliquid nonionic surfactant and having a pH, measured as a 1 percentaqueous solution, of about l 1.0.

2. The particulate free-flowing silicated sodium carbonate detergentbuilder produced by the method of claim 1 which is a substantiallyanhydrous coherent mixture of sodium carbonate and a sodium silicatehaving a Na2O:SiO2 ratio of 1:1.6 to 3.3, the amount of SiO2 beingwithin the range of 10 to 30 percent, said builder having a bulk densitywithin the range of 25 to 50 lbs./ft.3, being capable of absorbing up to15 percent of its weight of a liquid nonionic surfactant and having a pHlower than that of either the sodium silicate or sodium carbonate fromwhich it is formed.
 3. The particulate free-flowing silicated sodiumcarbonate detergent builder produced by the process of claim 1containing from 18 to 22 percent by weight SiO2, as sodium silicatehaving a Na2O:SiO2 weight ratio 1:2.4, said builder having a bulkdensity within the range of 35 to 50 lbs./ft.3, being capable ofabsorbing about 15 percent of its weight of a liquid nonionic surfactantand having a pH, measured as a 1 percent aqueous solution, of about11.0.